Aspergillus flavus and A. parasiticus are important fungal pathogens that infect a wide range of cereals, oil seeds and nuts. They produce toxic metabolites called aflatoxins (mycotoxins with carcinogenic and teratogenic properties) that can contaminate food products. Although strictly regulated around the world, aflatoxin contamination in developing countries is poorly regulated. In addition, limited management options and lack of agricultural resources have led to repeated outbreaks of acute aflatoxicosis, fatal to many. Two recent studies on strains of A. flavus may provide a new route for aflatoxin management.
In corn, the crop associated with recent epidemics in Kenya (2010, 2008, 2004-2006), A. flavus infects kernels causing Aspergillus ear rot. This disease can be caused by two specific strains of A. flavus – strain S that produces fewer spores, but higher aflatoxin and strain L that produces more spores but less aflatoxin. In a recent study, researchers Probst et al. studied the relative percentage of these two strains in different parts of Kenya. They found that in regions where aflatoxicosis outbreaks occurred frequently, like in the Eastern province, S strain was predominant in soil and corn samples. In neighboring provinces without such outbreaks however, much lower incidence of S strain was found suggesting that community structure of A. flavus might be a crucial factor influencing aflatoxicosis outbreaks.
In another study, Probst et al. studied the potential of native atoxigenic (lacking the ability to produce aflatoxin) L strains to serve as biocontrol agents. They found that 12 of their 96 atoxigenic isolates were able to reduce aflatoxin production by > 80% in corn kernels inoculated with a highly toxogenic S strain. Although such biological control isolates are currently available in US, introducing exotic strains is considered risky for multiple reasons. Thus the identification of better adapted, native isolates could provide a viable solution to low-income farmers of Kenya where pre-harvest aflatoxin management options are lacking.
- Probst, C.; Schulthess, F.; Cotty, P.J. (published online 7 July 2009) Impact of Aspergillus section Flavi community structure on the development of lethal levels of aflatoxins in Kenyan maize (Zea mays). Journal of Applied Microbiology. DOI: 10.1111/j.1365-2672.2009.04458.x
- Probst, C.; Bandyopadhyay, R.; Price, L.E.; Cotty, P.J. (February 2011) Identification of Atoxigenic Aspergillus flavus Isolates to Reduce Aflatoxin Contamination of Maize in Kenya. Plant Disease. DOI: 10.1094/PDIS-06-10-0438